Re: [PATCH 01/11] mm/ioremap: change the return value of io[re|un]map_allowed

[Kefeng Wang]

On 2022/8/4 23:42, Alexander Gordeev wrote:
> On Mon, Aug 01, 2022 at 10:40:19PM +0800, Baoquan He wrote:
>
> Hi Baoquan,
>
> > --- a/arch/arm64/mm/ioremap.c
> > +++ b/arch/arm64/mm/ioremap.c
> > @@ -3,19 +3,20 @@
> >   #include <linux/mm.h>
> >   #include <linux/io.h>
> >   
> > -bool ioremap_allowed(phys_addr_t phys_addr, size_t size, unsigned long prot)
> > +void __iomem *ioremap_allowed(phys_addr_t phys_addr, size_t size, unsigned long prot)
> >   {
> >   	unsigned long last_addr = phys_addr + size - 1;
> > +	int ret = -EINVAL;
> If ret variable is really needed?
>
> > diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> > index 72974cb81343..d72eb310fb3c 100644
> > --- a/include/asm-generic/io.h
> > +++ b/include/asm-generic/io.h
> > @@ -967,26 +967,27 @@ static inline void iounmap(volatile void __iomem *addr)
> >   /*
> >    * Arch code can implement the following two hooks when using GENERIC_IOREMAP
> >    * ioremap_allowed() return a bool,
> > - *   - true means continue to remap
> > - *   - false means skip remap and return directly
> > + *   - IS_ERR means return an error
> > + *   - NULL means continue to remap
> > + *   - a non-NULL, non-IS_ERR pointer is returned directly
> If ioremap_allowed() returns a valid pointer, then the function name
> is not as precise anymore.

Maybe use arch_ioremap/unmap as before, or some better name.

> > @@ -28,8 +29,11 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size,
> >   	phys_addr -= offset;
> >   	size = PAGE_ALIGN(size + offset);
> >   
> > -	if (!ioremap_allowed(phys_addr, size, prot))
> > +	base = ioremap_allowed(phys_addr, size, prot);
> > +	if (IS_ERR(base))
> >   		return NULL;
> > +	else if (base)
> > +		return base;
> It is probably just me, but the base name bit misleading here.
We could reuse vaddr, not add new base.
> > @@ -50,9 +54,9 @@ EXPORT_SYMBOL(ioremap_prot);
> >   
> >   void iounmap(volatile void __iomem *addr)
> >   {
> > -	void *vaddr = (void *)((unsigned long)addr & PAGE_MASK);
> > +	void __iomem *vaddr = (void __iomem *)((unsigned long)addr & PAGE_MASK);
> >   
> > -	if (!iounmap_allowed(vaddr))
> > +	if (iounmap_allowed(vaddr))
> I guess, iounmap_allowed() should accept void __iomem *, not void *.
> Then addr needs to be passed to iounmap_allowed() not vaddr.

The following is_vmalloc_addr()  and vunmap() in iounmap() use void *,

so we could simply use void* for iounmap_allowed().

> >   		return;
> .